(meth)acrylate copolymers and their use in nonlinear optics and for the production of langmuir-blodgett

ABSTRACT

Novel (meth)acrylate copolymers which contain, as polymerized units, 
     A) one or more (meth)acrylates and/or (meth)acrylamides having second order nonlinear optical properties and of the general formula I ##STR1##  where R is hydrogen or methyl, X is a flexible spacer, which may or may not be present, Y is a divalent group having electron donor activity and Z is a noncentrosymmetric radical containing an easily polarizable conjugated π-electron system and one or more electron acceptor groups, and 
     B) one or more (meth)acrylates of alkanols where the alkyl radical is of 10 to 30 carbon atoms 
     in a molar ratio of (A) to (B) of from 1:0.5 to 1:5 are very suitable as nonlinear optical materials for nonlinear optical arrangements and for the production of Langmuir-Blodgett films. The novel (meth)acrylate copolymers which contain terminal nitro, trifluoromethyl, cyano or fulven-6-yl groups as electron acceptors and have molar ratios A to B differing from those mentioned above are also suitable for intended uses outside nonlinear optics.

The present invention relates to novel (meth)acrylate copolymers whichhave nonlinear optical properties and which can form solid monomolecularLangmuir-Blodgett films.

The present invention furthermore relates to the use of the novel(meth)acrylate copolymers in nonlinear optics and Langmuir-Blodgettfilms which are obtained using the novel (meth)acrylate copolymers.

The present invention also relates to a novel process for the uniformspatial orientation of organic radicals.

Nonlinear optics is concerned very generally with the interaction ofelectromagnetic fields in different substances and the associatedfield-dependent refractive index in these substances.

Very generally, a substance emits light if dipoles oscillate in it, thefrequency of the emitted light wave being equal to the oscillationfrequency of the dipoles. If the oscillating dipoles contain a pluralityof frequency components, all of these occur in the light emitted by therelevant substance. If the dimensions of the substance are greater thanthe wavelength of the emitted light, the identical dipoles oscillatingin the substance should as far as possible oscillate in the samedirection and with a phase difference which ensures that the lightemitted by a volume element is not extinguished by destructiveinterference with the light emitted by another volume element.

In a polarizable substance, macroscopic polarization P, which is definedas the dipole moment per unit volume, is induced by an external electricfield

If the polarizable substance does not contain any permanent moleculardipoles, the dipole moment and hence the macroscopic polarization from ashift of the electrons by an amount d away from their rest position,i.e. from the center of the positive charge. On the other hand, if thepolarizable substance contains permanent dipoles, the applied electricfield E results in a change in the permanent dipole moment by the samemechanism.

As long as the shift d remains proportional to the electric field E, thepolarization P is also proportional to the electric field E, which isexpressed by the known linear equation 1

    P=ε.sub.0 χE                                   Equation 1.

In Equation 1, ε₀ is the absolute dielectric constant and χ is thedielectric susceptibility.

If the external electric field is increased, every substance must ofcourse exhibit a deviation from the linear law according to Equation 1above a field strength specific to it. The mechanical analog to this isthe deviation from Hook's law when a spring is overloaded. Suchdeviations from linearity are most simply handled mathematically byadding a parabolic term and higher powers of the variables, i.e. thenonlinear function is expanded by powers of the variable resulting inEquation 2

    P=ε.sub.0 (χ.sup.(1) E+χ.sup.(2) E+χ.sup.(2) EE+χ.sup.(3) EEE . . . )                              Equation 2

the fundamental equation of nonlinear optics. In this equation,

χ.sup.(1) is the first order dielectric susceptibility, which is finallyresponsible for linear optical behavior of the relevant substance,

χ.sup.(2) is the second order dielectric susceptibility, which inducessecond order nonlinear optical behavior in the relevant substance, and

χ.sup.(3) is the third order dielectric susceptibility, which isresponsible for the third order nonlinear optical behavior of therelevant substance.

Both χ.sup.(2) and χ.sup.(3) are material constants which are dependenton the molecular structure, the crystal structure, the frequency oflight and in general also the temperature. It is known that they can bedetermined by the dynamic holographic method of "four wave mixing", asdescribed by

W. W. Schkunow et al. in Spektrum der Wissenschaft, February 1986, pages92 to 97, and

J. P. Huignard et al. in SPIE Volume 215, Recent Advances in Holography,pages 178 to 182, 1980.

Substances having a dielectric susceptibility χ.sup.(2) dependent on thefield strength, i.e. having nonlinear second order optical properties,give rise to a number of dispersive processes, such as frequencydoubling (second harmonic generation, SHG), which permits the productionof light having half the wavelength of the incident light, theelectrooptical effect (Pockels' effect), which permits a change in therefractive index when an electric field is applied, or sum anddifference frequency mixing, and frequency mixing which permits thecontinuous adjustment of laser light, resulting in many technicalapplications. Examples are the electrooptical switches, frequency andintensity control in laser technology, and holography, informationprocessing and integrated optics.

Substances having a dielectric susceptibility χ.sup.(3) which isdependent on the field strength, i.e. having nonlinear third orderoptical properties, are suitable, inter alia, for the production ofpurely optical switches and hence as waveguides for the construction ofpurely optical computers.

Other possible applications are described in the publication by D. R.Ulrich, Nonlinear Optical Polymer Systems and Devices, in MolecularCrystals and Liquid Crystals, Volume 180, pages 1 to 31, 1988. Thisarticle also describes the growing importance of polymers havingnonlinear optical properties, which it is hoped will be distinguished byresponse times of less than one picosecond, high, nonresonantnonlinearity, low dielectric constant for direct current, low switchingenergies, a broad frequency range, low absorbance, the absence ofdiffusion problems, the possibility of resonance amplification, simpleproduction and processibility and the possibility of modification in asimple manner, good handling properties and the possibility of use atroom temperature, stability to environmental influences and mechanicaland structural stability, and will therefore increasingly replace thelong-known organic and inorganic crystalline substances having nonlinearoptical properties.

It is known that these polymers, like all substances, have the thirdorder nonlinear optical properties, whereas the second order nonlinearoptical properties are associated with the presence of anoncentrosymmetric molecular structure and/or a noncentrosymmetricmolecular arrangement in the crystals. Furthermore, a polymer must havea dielectric susceptibility χ.sup.(2) of not less than 10⁻⁸, preferably10⁻⁷, esu in order to be suitable for the abovementioned intended uses,which sets high requirements for the molecular structure of the polymersas such, their production and the uniform spatial orientability of thegroups present therein and having second order nonlinear opticalproperties. Only if these requirements are met can the other advantageswhich are peculiar to the polymers or which it is hoped they will havebe beneficially used or realized.

(Meth)acrylate or (meth)acrylamide polymers or copolymers which contain,as polymerized units, one or more (meth)acrylates and/or(meth)acrylamides having second order nonlinear optical properties andof the general formula I ##STR2## where R is hydrogen or methyl, X is aflexible spacer, which may or may not be present, Y is a divalent grouphaving electron donor activity and Z is a noncentrosymmetric radicalcontaining an easily polarizable conjugated π-electron system and one ormore terminal electron acceptor groups, are disclosed in U.S. Pat. No.4,755,574, U.S. Pat. No. 4,762,912, EP-A-0 271 730, WO 88/04305 andpublication by P. LeBarny et al., Some new side-chain liquid crystallinepolymers for nonlinear optics, in SPIE, Volume 682, Molecular andOptoelectronic Materials: Fundamentals and Applications, pages 56 to 64,1986. The uniform spatial orientation of the side groups, which isnecessary for utilizing their second order nonlinear optical properties,is achieved in these (meth)acrylate and (meth)acrylamide polymers andcopolymers through melting and glassy solidification of the polymers, inwhich the side groups, owing to their liquid crystalline properties, arespatially uniformly oriented, or through (co)polymerization of uniformlyspatially oriented (co)monomer films.

Furthermore, EP-A-0 271 730 discloses that the (meth)acrylates describedtherein and of the general formula I can be copolymerized with vinylmonomers, such as an alkyl (meth)acrylate. However, specific alkyl(meth)acrylates are not mentioned, nor are the amounts in which they areto be used stated.

WO 88/04305 discloses that the (meth)acrylates or (meth)acrylamidesdescribed therein and of the general formula I can be copolymerized withone or more (meth)acrylates of an alkanol where the alkyl radical is of1 to 20, preferably from 4 to 8, carbon atoms. However, ratios are notstated, and the examples describe only copolymers of4-{2-[4-(6-methacryloyloxyhexyloxy)-phenyl]-ethenyl}-pyridine or4-[4-(6-methacryloyloxyhexyloxy)-phenyl]-pyridine with2-[4-(4'-cyanobiphenyl-4-yloxycarbonyl)-phenoxy]-ethyl methacrylate.Furthermore, the radicals Z of the (meth)acrylates or (meth)acrylamidesof the general formula I of WO 88/04305 contain no terminal nitro,trifluoromethyl, cyano or fulven-6-yl groups as electron acceptors.

Solid monomolecular films are likewise known. They are formed bycompounds which have a polar and therefore hydrophilic molecular end anda nonpolar and therefore hydrophobic long-chain radical. Compounds ofthis type are generally also referred to as amphiphiles. For filmformation, the amphiphiles are applied to a water surface, over whichthey spread, their polar end dipping into the aqueous phase and theirhydrophobic long-chain radicals projecting out of the aqueous phase. Ifthe compounds are then pushed together on the water surface by means ofa barrier, above a certain surface pressure they arrange themselves intoa solid monomolecular film in which the hydrophobic long-chain radicalsare uniformly spatially oriented. The transformation into such a solidmonomolecular film is evident, in the form of a sharp pressure increase,in the pressure/area graph recorded during pushing together of therelevant compound. This pressure increase is a result of the increasedresistance of the now solid monomolecular film to further compression bythe barrier.

The solid monomolecular film produced in this manner can be drawn ontothe surface of substrates in a simple manner. This is effected, forexample, by immersing the substrate in the aqueous phase and withdrawingit again, with the result that the solid monomolecular film istransferred from the water surface to the substrate surface; forexample, from hydrophobic surfaces, such as pure silicon surfaces, thenonpolar molecular ends of the compounds adhere to the substratesurface. Complete transfer is generally referred to in terms of atransfer ratio of 1.

One or more further layers of this type can be drawn onto the surface ofthe solid monomolecular film present on the substrate. Usually, thisfurther solid monomolecular film is applied to the first film in such away that the polar molecular ends of the compounds of both films faceone another This spatial arrangement is also referred to ashead-head-tail-tail orientation or as Y deposition. If a third film isapplied to this double film, it is arranged in a corresponding manner,so that its hydrophobic long-chain radicals face the relevant radicalsof the second film, whereas their polar molecular ends point outward.

If the compounds which form these solid monomolecular multilayers have apermanent dipole moment, the Y deposition results in macroscopicpolarization P, which is due only to the uppermost of the films, only inthe case of an odd number of films one on top of the other. For an evennumber, of course, a macroscopic polarization P of zero results becausethe dipole moments of the individual films cancel one another owing totheir opposite orientation.

If, on the other hand, in the case of a solid monomolecular multilayerapplied in Y deposition, it is intended to achieve, at leastapproximately, the maximum possible macroscopic polarization P, solidmonomolecular films of compounds without a dipole moment must beintercalated in Y deposition between the individual films of compoundshaving a permanent dipole, resulting in an alternating film sequence inwhich all permanent dipoles present are uniformly oriented.

It is known that both the solid monomolecular monolayers and thecorresponding multilayers are referred to as Langmuir-Blodgett films.The process for their production and the apparatuses used for thispurpose are usually summarized by the standard technical termLangmuir-Blodgett technology. For the sake of brevity, only thesetechnical terms will be used below.

Langmuir-Blodgett films which are formed by (meth)acrylate copolymerswhich have side groups which possess liquid-crystalline, nonlinearoptical properties are disclosed in the publication by M. M. Carpenteret al., The Characterization of Langmuir-Blodgett Films of a Non-LinearOptical, Side Chain Liquid Crystalline Polymer, in Thin Solid Films 161(1988), 315-324. However, these are not copolymers of a (meth)acrylateof the general formula I with alkyl (meth)acrylates but are thecopolymer shown below: ##STR3##

Although the side groups of this copolymer can be uniformly spatiallyoriented by means of Langmuir-Blodgett technology, the polymer is notobtainable in a simple manner.

The (meth)acrylate copolymers and Langmuir-Blodgett films known to datedo not yet meet all the requirements set in practice for the productionand the uniform spatial orientability of polymers having second ordernonlinear optical properties. With the (meth)acrylate copolymers knownto date, it is therefore not possible to realize the abovementionedadvantages expected of polymers having nonlinear optical properties tothe extent and with the reliability absolutely essential for technicaluse.

It is an object of the present invention to provide novel (meth)acrylatecopolymers which do not have the disadvantages of the prior art andwhose side groups having second order nonlinear optical properties canbe uniformly spatially oriented in a simple and reliable manner, so thatthe novel (meth)acrylate copolymers can be used as nonlinear opticalmaterials in nonlinear optical arrangements.

We have found that this object is essentially achieved, surprisingly, if(meth)acrylates and/or (meth)acrylamides of the abovementioned generalformula I are copolymerized in certain defined molar ratios with one ormore (meth)acrylates of alkanols where the alkyl radical is of 10 to 30carbon atoms, and the resulting copolymers are then formed intoLangmuir-Blodgett films by means of Langmuir-Blodgett technology.

The present invention accordingly relates to (meth)acrylate copolymerswhich contain, as polymerized units,

(A) one or more (meth)acrylates and/or (meth)acrylamides having secondorder nonlinear optical properties and of the general formula I ##STR4##where R is hydrogen or methyl, X is a flexible spacer, which may or maynot be present, Y is a divalent group having electron donor activity andZ is a noncentrosymmetric radical containing an easily polarizableconjugated π-electron system and one or more terminal electron acceptorgroups, and

B) one or more (meth)acrylates of alkanols where the alkyl radical is of10 to 30 carbon atoms,

in a molar ratio of (A) to (B) of from 1:0.5 to 1:5.

In view of the prior art cited at the outset, it was not to be expectedthat the novel (meth)acrylate copolymers, which can be simply preparedand furthermore have the high second order dielectric susceptibilityχ.sup.(2) of from >10⁻⁸ to 10⁻⁷ esu, which is required for use, can alsobe uniformly spatially oriented in a particularly simple manner withouthaving to rely for this purpose on side groups which have liquidcrystalline properties and are difficult to prepare or on methods forforced uniform spatial orientation.

The novel (meth)acrylate copolymers contain the (meth)acrylates and/or(meth)acrylamides (A) having second order nonlinear optical propertiesand of the general formula I and the (meth)acrylates (B) in a molarratio of (A) to (B) of 1:0.5 to 1:5, as polymerized repeating units.

It is possible to use molar ratios (A):(B) greater than 1:0.5, forexample from 1:0.4 to 1 0.1, but the side radicals or side groups--CO--X--Y--Z or --CO--Y--Z of the (meth)acrylates or of the(meth)acrylamides (A) of the general formula I then sometimes can nolonger be reliably uniformly spatially oriented.

If, on the other hand, molar ratios (A):(B) of less than 1:5, forexample from 1:6 to 1:20, are chosen, the nonlinear optical propertiesof the relevant (meth)acrylate copolymers sometimes cannot fully meetall requirements in practice.

Accordingly, the molar ratio (A):(B) of from 1:0.5 to 1:5 to be usedaccording to the invention is an optimum range within which the molarratios can be freely selected and adapted in an outstanding manner tothe particular (meth)acrylates and/or (meth)acrylamides (A) used and tothe (meth)acrylates (B) and to the particular intended use.

Within this optimum range, the molar ratios (A):(B) of from 1 0.9 to 1 4are particularly noteworthy because such molar ratios result in novel(meth)acrylate copolymers which, on the one hand, have second ordernonlinear optical properties which are suitable in practice and, on theother hand, can be particularly excellently formed, by means ofLangmuir-Blodgett technology, into Langmuir-Blodgett films in which allside groups --CO--X--Y--Z or CO--Y--Z of the general formula I areuniformly spatially oriented, which is essential especially with regardto the use of the relevant novel (meth)acrylate copolymers as nonlinearoptical materials.

The novel (meth)acrylate copolymers can contain, as polymerized units,only the (meth)acrylates and/or the (meth)acrylamides (A) of the generalformula I and the (meth)acrylates (B). For specific intended uses,however, they may contain further (meth)acrylate, (meth)acrylamide,vinylaromatic, vinyl halide, vinyl ester, vinyl ether, allyl ester,allyl ether, alkene or alkadiene comonomers or acrylonitrile aspolymerized units. These comonomers may carry dichroic chromophores ormesogenic groups, i.e. groups having liquid-crystalline properties. Inthis context, reference may be made to the prior art cited at the outsetor to EP-A-0 184 482, EP-A-0 228 703, EP-A-0 258 898, DE-A-36 03 267 orDE-A36 31 841, which disclose further such comonomers. If such furthercomonomers are contained as polymerized units in the novel(meth)acrylate copolymers, they are present in molar ratios which do notreduce the particular advantages of the novel (meth)acrylate copolymers.

Regardless of whether the novel (meth)acrylate copolymers containfurther comonomers as polymerized units, the molar ratio (A):(B) iswithin the above-mentioned limits.

The novel (meth)acrylate copolymers which contain, as polymerized units,only one or more (meth)acrylates or (meth)acrylamides (A) having secondorder nonlinear optical properties and of the general formula I and oneor more (meth)acrylates (B) are preferred according to the invention.

Examples of suitable flexible spacers X which may be used for the(meth)acrylates and/or (meth)acrylamides (A) of the general formula Iwhich are to be employed according to the invention and have secondorder nonlinear optical properties are substituted or unsubstituted1-oxaalkanediyl groups whose carbon chains may be interrupted by heteroatoms, such as oxygen, nitrogen, phosphorus or sulfur. The1-oxaalkanediyl groups advantageously contain 2 to 12, in particular 2to 6, carbon atoms. Examples of particularly suitable spacers X are1-oxapropane-1,3-diyl, 1-oxabutane-1,4-diyl, 1-oxapentane-1,5-diyl,1-oxahexane-1,6-diyl and 1-oxaheptane-1,7-diyl, of which1-oxapropane-1,3-diyl and 1-oxaheptane-1,7-diyl are particularlypreferred. Frequently, the 1-oxadodecane1,12-diyl group also proves veryparticularly advantageous.

Examples of suitable divalent groups Y having electron donor activityfor the (meth)acrylates and/or (meth)acrylamides (A) of the generalformula I which are to be employed according to the invention and havesecond order nonlinear optical properties are ether, thioether, amino orN-alkylamino groups, --N--(alkyl)-- or the groups ##STR5## of which theether, amino and N-alkylamino groups, --N--(alkyl)--, in particularN-methylamino, and piperazine-1,4-diyl are particularly preferred.

Examples of suitable noncentrosymmetric radicals Z, containing an easilypolarizable conjugated π-electron system and one or more terminalelectron acceptor groups, for the (meth)acrylates and (meth)acrylamides(A) of the general formula I which are to be employed according to theinvention and have second order nonlinear optical properties are##STR6## where n is an integer of from 1 to 22, A.sup.⊖ is aconventional acid anion, such as Cl.sup.⊖, Br.sup.⊖ or HSO₄.sup.⊖,##STR7##

Examples of suitable radicals Z are those which contain nitro, cyano,trifluoromethyl or fulven-6-yl as the terminal electron acceptor group,since the novel (meth)acrylate copolymers which contain, as polymerizedunits, one or more (meth)acrylates and/or (meth)acrylamides (A) of thegeneral formula I having one of these suitable radicals Z and one ormore (meth)acrylates (B) have, in the case of molar ratios (A):(B)greater than 1:0.5 and less than 1:5, properties which make the relevant(meth)acrylate copolymers also suitable for intended uses outsidenonlinear optics, in the field of molding production.

Examples of suitable radicals -X-Y-Z or -Y-Z for the (meth)acrylatesand/or (meth)acrylamides (A) of the general formula I which are to beemployed according to the invention and have second order nonlinearoptical properties, which radicals consist of the abovementionedexamples of flexible spacers X, divalent groups Y having electron donoractivity and radicals Z or only of the abovementioned examples of Y andZ, are disclosed in U.S. Pat. No. 4,694,066 (EP-A-0 235 506), U.S. Pat.No. 4,762,912, U.S. Pat. No. 4,755,574, WO 88/04305, EP-A-0 271 730 orthe publications by M. M. Carpenter et al., in Thin Solid Films 161(1988), 315-324, and P. LeBarny et al. in SPIE, Volume 682, Molecularand Polymeric Optoelectronic Materials: Fundamentals and Applications,pages 56 to 64, 1986.

Examples of suitable (meth)acrylates and (meth)acrylamides (A), havingsecond order nonlinear properties and of the general formula I, for thepreparation of the novel (meth)acrylate copolymers and of theirpreparation are disclosed in the two abovementioned publications by M.M. Carpenter et al. on the one hand and P. LeBarny on the other hand andin EP-A-0 271 730, WO 88/04305, U.S. Pat. No. 4,762,912 or U.S. Pat. No.4,755,574.

Examples of particularly suitable (meth)acrylates and (meth)acrylamides(A), having second order nonlinear optical properties and of the generalformula I, which are particularly advantageously used for thepreparation of the novel (meth)acrylate copolymers are2-[N-(p-nitrophenyl)-N-methylamino]-ethyl methacrylate and thecorresponding acrylate, 4-(p-nitrophenylazo)-methacrylanilide and thecorresponding acrylanilide,11-[4-(p-nitrophenyl)-piperazin-1-yl]-undecyl methacrylate and thecorresponding acrylate,4-nitro-4'-[N-methyl-N-(11-methacryloyloxyundec-1-yl)-amino]-azobenzeneand the corresponding acrylate and4,-[N-methyl-N-(11-methacryloyloxyundec-1-yl)-amino]-benzaldehyde-4-nitrophenylhydrazoneand the corresponding acrylate, of which the methacrylic derivatives arepreferred.

Examples of suitable (meth)acrylates (B) of alkanols where the alkylradical is of 10 to 30 carbon atoms are n-decyl, n-undecyl, n-dodecyl,n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl,n-octadecyl, n-nonadecyl, n-eicosanyl, n-C₂₁ H₄₃, n-C₂₂ H₄₅, n-C₂₃ H₄₇,n-C₂₄ H₄₉, n-C₂₅ H₅₁, n-C₂₆ H₅₃, n-C₂₇ H₅₅, n-C₂₈ H₅₇, n-C₂₉ H₅₉ orn-C₃₀ H₆₁ acrylate or methacrylate. Among these, the (meth)acrylates (B)whose alkyl ester radicals (--COO--alkyl) have roughly the same or thesame length as the radicals --CO--X--Y--Z or --CO--Y--Z of the(meth)acrylates and (meth)acrylamides (A) of the general formula I aresuitable, the methacrylates (B) being particularly suitable andn-heptadecyl, n-octadecyl and n-nonadecyl methacrylate being veryparticularly suitable. Among the last-mentioned ones, n-octadecylmethacrylate is preferably used.

The novel (meth)acrylate copolymers have a number average molecularweight M_(n) of from 1,000 to 50,000, preferably from 2,000 to 20,000,in particular from 3,000 to 10,000. Their second order dielectricsusceptibility determined by four wave mixing is greater than χ.sup.(2)=10⁻⁸, in particular 10⁻⁷ esu. A very particular advantage of the novel(meth)acrylate copolymers is that the second order dielectricsusceptibility χ.sup.(2) can be established and further increased in asimple manner by the uniform spatial orientation of their side groups inLangmuir-Blodgett monolayers and multilayers.

The preparation of the novel (meth)acrylate copolymers has no specialfeatures in terms of the method but is carried out by the conventionaland known methods of free radical polymerization and copolymerization,as described in, for example, U.S. Pat. No. 4,762,912, U.S. Pat. No.4,755,574, EP-A-0 271 730, WO 88/04305 or the abovementionedpublications by M. M. Carpenter et al. and P. LeBarny et al.

The novel (meth)acrylate copolymers are very useful for production ofnonlinear optical materials which either consist of the novel(meth)acrylate copolymers or which contain further components over andabove these.

In particular, the novel (meth)acrylate copolymers are suitable for theproduction of Langmuir-Blodgett mono- and multilayers which eitherconsist only of the novel (meth)acrylate copolymers or which, in thecase of the multilayers, contain further different Langmuir-Blodgettfilms applied in Y deposition, in alternating sequence.

Particularly preferred Langmuir-Blodgett multilayers are those whichcontain Langmuir-Blodgett monolayers of one or more of the novel(meth)acrylate copolymers and Langmuir-Blodgett monolayers of one ormore polymeric amphiphiles, applied in Y deposition and in alternatingsequence.

An example of a particularly suitable polymeric amphiphile is ##STR8##

The production of these novel Langmuir-Blodgett mono- and multilayershas no special features in terms of the method but is carried out by theconventional and known Langmuir-Blodgett technology described at theoutset.

The organic radicals or side groups in the novel (meth)acrylatecopolymers prove to be particularly easy to orient uniformly spatiallywithout having to rely on side groups which have liquid crystallineproperties and are difficult to prepare or on methods for their forceduniform spatial orientation. In view of the use of the novel(meth)acrylate copolymers and of the novel Langmuir-Blodgett films asnonlinear optical materials, this is a very particular advantage.

If it is necessary during or after the uniform spatial orientation ofthe organic radicals in the novel (meth)acrylate copolymers by theLangmuir-Blodgett technology, the novel Langmuir-Blodgett mono- andmultilayers can be produced with the aid of electric and/or magneticfields of suitable direction and suitable sign and/or, after theirproduction, can be subjected, if necessary in these fields, toconventional and known processes for domain growth, for examplerecrystallization or zone melting.

Accordingly, the novel (meth)acrylate copolymers are very useful for theproduction of novel nonlinear optical arrangements as used, for example,for frequency doubling, frequency mixing or optical waveguides or aspresent in optical modulators, optical multiplexers, optical logicmodules or optical amplifiers.

These novel nonlinear optical arrangements contain one or moresubstrates adapted to the corresponding intended use in form andfunction, for example a semiconductor chip, and one or more films, inparticular a Langmuir-Blodgett film, which contains or consists of oneor more novel (meth)acrylate copolymers.

When they are used in nonlinear optical arrangements, further particularadvantages of the novel (meth)acrylate copolymers and of the novelLangmuir-Blodgett films become evident: for example, their exacttwodimensional orientation results in uniform thickness and the maximumpossible anisotropy of the relevant films. Moreover, said films arestable to intense laser radiation.

EXAMPLES EXAMPLE 1 Preparation of a novel methacrylate copolymer using amethacrylamide (A) having a radical --CO--Y--Z of the general formula Iand n-octadecyl methacrylate (B)

Experimental method:

1. Preparation of 4-(p-nitrophenylazo)-methacrylanilide[(meth)acrylamide (A)]

4 g of 4-amino-4'-nitroazobenzene in 150 ml of chloroform were addeddropwise to 1.71 g of methacryloyl chloride and 1.65 g of triethylaminein 20 ml of chloroform while cooling with ice water. After the addition,the resulting reaction mixture was first stirred for 2 hours at roomtemperature and then refluxed for 3 hours. Thereafter, a further 0.85 gof methacryloyl chloride and 0.82 g of triethylamine in 10 ml ofchloroform were added, after which the reaction mixture was refluxed for8 hours. After the mixture had cooled to room temperature, excessmethacryloyl chloride was distilled off. The product solution wasdiluted with 30 ml of chloroform, after which 100 1 (sic) of water wereadded and washing was then carried out with a further two portions of100 ml of water. The aqueous phases were separated off and the productsolution was then dried with Na₂ SO₄. Thereafter,4-(p-nitrophenylazo)methacrylanilide was isolated by evaporating thechloroform and was then purified by column chromatography over silicagel 60 using ethyl acetate/hexane in a volume ratio of 3:7 as the mobilephase. 0.95 g of the product which had the following physical propertieswas obtained: melting point: 210° C.; IR spectrum (KBr pellet): bands at3,400, 2,900, 2,850, 1,690, 1,680, 1,590, 1,510, 1,340, 1,140, 1,110 and840 cm⁻¹ ; ¹ H nuclear magnetic resonance spectrum (400 MHz, CDCl₃,tetramethylsilane as internal standard), chemical shift δ (in ppm): 8.37(doublet, 2H), 8.0 (multiplet, 4H), 7.8 (doublet, 2H), 7.73 (singlet,1H), 5.86 (singlet, 1H), 5.55 (singlet, 1H), 2.12 (singlet, 3H).

2. Preparation of the novel methacrylate copolymer

0.013 g of azobisisobutyronitrile was added to 0.87 g of n-octadecylmethacrylate and 0.4 g of 4-(p-nitrophenylazo)-methacrylanilide, afterwhich the resulting reaction solution was flushed for 1 hour withnitrogen. Thereafter, the reaction solution was kept at 70° C. for 5days, a further 0.013 g of azobisisobutyronitrile being metered in every24 hours. The reaction solution was then evaporated down and themethacrylate copolymer was precipitated in methanol, purified byrepeated reprecipitation from toluene with methanol and then dried. 0.3g of the novel methacrylate copolymer, having a number average molecularweight M_(n) of 5,500 and a molar ratio (A):(B) of 1:3.9 determined byelemental analysis, was obtained The product, in the form of a film, hadthe following bands in its IR spectrum: 2,900, 2,850, 1,720, 1,690,1,590, 1,510, 1,450, 1,340, 1,240, 1,170 and 1,140 cm⁻¹.

The novel methacrylate copolymer was very suitable for the production ofnonlinear optical materials and of Langmuir-Blodgett films.

EXAMPLE 2 Preparation of a novel methacrylate copolymer using amethacrylate (A) having a radical --CO--X--Y--Z according to the generalformula I and n-octadecyl methacrylate (B)

Experimental method:

1. Preparation of 2-[N-(p-nitrophenyl)-N-methylamino]-ethanol

5.25 g of N-methylethanolamine, 11.2 g of p-nitrofluorobenzene, 9.7 g ofK₂ CO₃ and 2 drops of tricaprylmethylammonium chloride in 70 ml ofdimethylformamide were heated at 95° C. for 3 days. The resultingreaction mixture was poured onto 350 ml of water. The precipitatedproduct was filtered off under suction, after which the aqueous phasewas extracted with toluene. After drying and evaporating down thetoluene solution, the two product fractions were combined andrecrystallized from ethanol/water in a volume ratio of 2 1. 10.22 g of2-[N-(p-nitrophenyl)-N-methylamino]-ethanol having the followingphysical properties were obtained: melting point: 99°-101° C., IRspectrum (KBr pellet): bands at 3,450, 2,900, 2,850, 1,690, 1,680,2,900, 1,580, 1,470, 1,450, 1,330, 1,320, 1,110, 1,060 and 825 cm⁻¹ ; ¹H nuclear magnetic resonance spectrum (400 MHz, CDCl₃, tetramethylsilaneas internal standard, chemical shift δ (in ppm): 8.05 (doublet, 2H),6.64 (doublet, 2H), 3.9 (triplet, 2H), 3.65 (triplet, 2H), 3.15(singlet, 3H) 2.02 (singlet, 1H).

2. Preparation of 2-[N-(p-nitrophenyl)-N-methylamino]-ethyl methacrylate{(meth)acrylate (A)}

2.67 g of methacryloyl chloride in 5 ml of chloroform were addeddropwise to 5 g of 2-[N-(p-nitrophenyl)-N-methylamino]-ethanol and 2.02g of pyridine in 40 ml of chloroform while cooling. Thereafter, theresulting reaction solution was first stirred at room temperature andthen refluxed for 3.5 hours. It was cooled to room temperature and then40 ml of water were added to it, after which the chloroform phase wasseparated off and the aqueous phase was extracted with three times 20 mlof chloroform. After the combined chloroform phases had been dried withNa₂ SO₄ and the chloroform evaporated off, the resulting product waswashed with hexane and dried under reduced pressure. 2.6 g of2-[N-(p-nitrophenyl)-N-methylamino]-ethyl methacrylate were obtained,the IR spectrum of the product in the form of a KBr pellet having bandsat 2,950, 2,900, 1,720, 1,600, 1,510, 1,490, 1,320, 1,310, 1,160, 1,110and 825 cm⁻¹.

3. Preparation of the novel methacrylate copolymer

0.93 g of 2-[N-(p-nitrophenyl)-N-methylamino]-ethyl methacrylate, 1.19 gof n-octadecyl methacrylate and 0.022 g of azobisisobutyronitrile weredissolved in 30 ml of toluene. The reaction solution was degassed bypassing in nitrogen for one hour and then kept at 70° C. for 3 days inthe absence of air, a further two portions of 0.021 g ofazobisisobutyronitrile being metered in. The reaction solution was thenevaporated down, after which the methacrylate copolymer was precipitatedby adding methanol. After repeated reprecipitation from toluene bymethanol, 0.93 g of the novel methacrylate copolymer having a numberaverage molecular weight M_(n) of 6,100 and a molar ratio (A):(B) of1:1.3, determined by elemental analysis, was obtained. The product hadthe following physical properties: IR spectrum (KBr pellet): bands at2,900, 2,860, 1,720, 1,595, 1,510, 1,490, 1,320, 1,160 and 1,110 cm⁻¹ ;¹ H nuclear magnetic resonance spectrum (400 MHz, CDCl₃,tetramethylsilane as internal standard), chemical shift δ (in ppm): 8.13(doublet), 6.75 (doublet), 3.93 (multiplet, unresolved), 3.75(multiplet, unresolved), 3.1 (singlet), 1.6 (multiplet, unresolved),1.22 (multiplet, unresolved), 0.88 ppm (triplet).

The novel methacrylate copolymer was easy to process, transparent,homogeneous and laser-stable in the form of a thin film and verysuitable for the production of Langmuir-Blodgett films.

EXAMPLE 3 Preparation of a novel methacrylate copolymer using amethacrylate (A) having a radical --CO--X--Y--Z according to the generalformula I and n-octadecyl methacrylate (B)

Experimental method:

1. Preparation of N-(11-hydroxyundecyl)-N'-(4-nitrophenyl)-piperazine

10 g of 11-bromoundecan-1-ol, 4 g of dry potassium carbonate powder,8.27 g of 4-nitrophenylpiperazine and 2 drops of the conventional andknown phase transfer catalyst Aliquat® 336 in 50 ml ofdimethylpropyleneurea were heated at 85° C. for 6 hours and then left tostand for 2 days. The reaction mixture was then poured into 500 ml ofwater. The precipitated crude product was filtered off under suction(first fraction). The water phase was extracted a further three timeswith 50 ml of toluene in each case and four times with 50 ml of ethylacetate in each case. The combined extracts were evaporated down and theremaining crude product fraction (second fraction) was combined with thefirst fraction, after which the combined crude product fractions wererecrystallized from a mixture of ethanol and water in a volume ratio of2:1. The recrystallized product was dried under reduced pressure, afterwhich 7.8 g of N-(11-hydroxyundecyl)-N'-(4-nitrophenyl)-piperazineresulted. The product had the following physical properties: meltingpoint 118° C., IR spectrum (KBr pellet): bands at 3,550, 2,900, 2,850,1,595, 1,575, 1,470, 1,333, 1,255, 1,250, 1,115, 820 and 750 cm⁻¹ ;elemental analysis: calculated 66.8% C, 9.34% H, 11.13% N and 12.7% O;found: 66.8% C, 9.4% H, 11.1% N and 12.7% O.

2. Preparation of 11-[4-(p-nitrophenyl)-piperazin-1-yl]-undecylmethacrylate

This methacrylate was prepared essentially as described in Example 2,Section 2, except thatN-(11-hydroxyundecyl)-N'-(4-nitrophenyl)-piperazine was used instead of2-[N-(p-nitrophenyl)-N-methylamino]-ethanol.

The elemental composition of the product, determined by chemicalanalysis, corresponded exactly to the theoretical calculations. It hadthe following ¹ H nuclear magnetic resonance spectrum (400 MHz, CDCl₃,tetramethylsilane as internal standard): chemical shift δ (in ppm):1.3-1.65 (multiplet, 18H), 1.95 (singlet, 3H), 2.6 (triplet, 4H), 3.45(triplet, 4H), 4.15 (triplet, 2H), 5.5 (doublet, 2H), 6.1 (doublet, 2H),6.8 (doublet, 2H) and 8.1 (doublet, 2H).

3 Preparation of the novel methacrylate copolymer

1 g of 11-[4-(p-nitrophenyl)-piperazin-1-yl]-undecyl methacrylate, 0.75g of n-octadecyl methacrylate and 0.0176 g of azobisisobutyronitrilewere dissolved in 25 ml of analytically pure toluene. The reactionsolution was degassed by passing in nitrogen for one hour and then keptat 70° C. for 5 days in the absence of air, a further 0.0175 g ofazobisisobutyronitrile being metered in daily. The reaction solution wasthen evaporated down, after which the methacrylate copolymer wasprecipitated by adding methanol. After repeated reprecipitation fromtetrahydrofuran by methanol, 0.86 g of the novel methacrylate copolymerhaving a number average molecular weight of M_(n) of 7,900 and a molarratio (A):(B) of 1:1.03, determined by elemental analysis, was obtained.The spectroscopic properties of the novel methacrylate copolymercorresponded to the theoretical expectations.

The novel methacrylate copolymer was easy to process, transparent,homogeneous and laser-stable in the form of a thin film and verysuitable for the production of Langmuir-Blodgett films.

EXAMPLE 4 Preparation of a novel methacrylate copolymer using amethacrylate (A) having a radical --CO--X--Y--Z according to the generalformula I and n-octadecyl methacrylate (B)

Experimental method:

1. Preparation of4'-[N-methyl-N-(11-hydroxyundecyl)-amino]-4-nitroazobenzene

12.5 g of 11-bromoundecan-1-ol in 40 ml of toluene were added dropwiseto 5.1 g of N-methylaniline in 5.1 g of triethylamine and 20 ml oftoluene at 85° C. while stirring. Stirring was continued for a further 5hours at 85° C., after which the resulting precipitate was filtered offunder suction. The filtrate separated was evaporated down and theresidue was dried under reduced pressure from an oil pump. 9.5 g ofcrude N-methyl-N(11-hydroxyundecyl)-aniline were further processedimmediately in the following manner:

The diazonium salt was prepared at -10° C. from 5.3 g of 4-nitroanilineand sodium nitrite in 19 ml of concentrated hydrochloric acid and 4 mlof water. Excess sodium nitrite was destroyed with 1.9 g of urea. Asuspension of N-methyl-N-(11-hydroxyundecyl)-aniline in 5.7 ml ofconcentrated hydrochloric acid and 28.5 ml of water was added dropwiseat -10° C. The resulting reaction mixture was heated to room temperatureafter 45 minutes and brought to pH 4 with potassium acetate. Theprecipitate which separated out was filtered off under suction afterstanding for 30 minutes and then washed neutral with water. Theresulting crude product was recrystallized from a mixture of heptane andethanol in a volume ratio of 9:1, 9.1 g of4'-[N-methyl-N-(11-hydroxyundecyl)-amino]-4-nitroazobenzene beingobtained, which corresponded to a yield of 63% of theory.

2. Preparationof4-nitro-4'-[N-methyl-N-(11-methacryloyloxyundec-1-yl)-amino]-azobenzene

The 4'-[N-methyl-N-(11-hydroxyundecyl)-amino]-4-nitroazobenzene obtainedin process step 1 was reacted with methacryloyl chloride according tothe method stated in Example 2, Section 2, to give4-nitro-4'-[N-methyl-N-(11-methacryloyloxyundec-1-yl)-amino]-azobenzene[methacrylate (A)]. The resulting product had the followingphysicochemical properties: IR spectrum (KBr pellet): bands at 2,900,2,850, 1,705, 1,585, 1,490, 1,325, 1,120, 1,150, 1,095, 850 and 810 cm⁻¹; ¹ H nuclear magnetic resonance spectrum (400 MHz, CDCl₃,tetramethylsilane as internal standard, chemical shift δ (in ppm): 1.3to 1.65 (multiplet, 18H), 1.9 (singlet, 3H), 3.1 (singlet, 3H), 3.4(triplet, 2H), 4.3 (triplet, 2H), 5.6 (singlet, 1H), 6.1 (singlet, 1H),6.7 (doublet, 2H), 7.9 (doublet, 4H), 8.3 (doublet, 2H); elementalanalysis: calculated: 67.3% C, 8.03% H, 13.13% N, 11.25% 0; found: 66.1%C, 7.7% H, 13.8% N, 12.1% 0.

3. Preparation of the novel methacrylate copolymer

0.38 g of4-nitro-4'-[N-methyl-N-(11-methacryloyloxyundec-1-yl)-amino]-azobenzene,0.52 g of n-octadecyl methacrylate and 0.009 g of azobisisobutyronitrilewere dissolved in 16 ml of analytically pure toluene. The resultingreaction solution was degassed by passing in nitrogen for one hour. Itwas then polymerized under a gentle stream of nitrogen in the course of8 hours at 70° C. Thereafter, a further six portions of 0.009 g ofazobisisobutyronitrile were metered in, the reaction mixture being keptat 70° C. for 8 hours after each addition. The reaction mixture was thenfiltered and the products present in the filtrate were precipitated withmethanol and separated off. The novel methacrylate copolymer obtainedwas washed with a few drops of acetone and then reprecipitated twicefrom toluene with methanol

0.17 g of the purified novel methacrylate copolymer was obtained. Thishad a number average molecular weight of M_(n) 8,400 and a molar ratio(A):(B) of 1:2.78, determined by elemental analysis. The spectroscopicproperties of the novel methacrylate copolymer corresponded to thetheoretical expectations.

This novel methacrylate copolymer, too, was easy to process,transparent, homogeneous and laser-stable in the form of a thin film andvery suitable for the production of Langmuir-Blodgett films.

EXAMPLE 5 Preparation of the novel methacrylate copolymer using amethacrylate (A) having a radical --CO--X--Y--Z according to the generalformula I and n-octadecyl methacrylate (B)

Experimental method:

1. Preparation of N-methyl-N-(11-hydroxyundecyl)-amine

A mixture of 5.8 g of N-methylformamide, 13.6 g of sodium hydroxidesolution powder [sic], 5.8 g of potassium carbonate powder, 3.2 g oftetrabutylammonium bisulfate and 90 ml of dimethylpropyleneurea wasstirred for 1 hour at room temperature. Thereafter, the resultingmixture was heated at 40° C. for 20 minutes and then to 70° C. At thistemperature, a solution of 25 g of 11-bromoundecan-1-ol in 70 ml ofdimethylpropyleneurea was added dropwise to the mixture. The resultingreaction mixture was then stirred for a further 12 hours at 70° C. andthen poured onto 1.6 1 of water. The aqueous phase obtained wasextracted with four times 180 ml of a solvent mixture of ether and ethylacetate in a volume ratio of 1 1. The resulting organic phases werecombined, and the combined organic phase was washed with three times 50ml of water and then dried with sodium sulfate. After the sodium sulfatehad been separated off and the organic solvent evaporated off, 20.5 g ofN-methyl-N-(11-hydroxyundecyl)-formamide were obtained, whichcorresponded to a yield of 91%.

The total amount of bisalkylated formamide in 100 ml of methanol and 40ml of concentrated hydrochloric acid was refluxed for 8 hours. Aftercooling, the reaction mixture was brought to pH 13 with 10% strengthsodium hydroxide solution and then extracted with three times 80 ml of asolvent mixture of ether and ethyl acetate in a volume ratio of 1:1. Thecombined organic phases were then washed with three times 30 ml of waterand then dried with sodium sulfate After the sodium sulfate had beenseparated off, the organic solution was evaporated down and theresulting N-methyl-N-(11-hydroxyundecyl)-amine was recrystallized fromn-heptane. 11.3 g of a purified product were obtained In the form of aKBr pellet, this had the following IR spectrum: bands at 3,350, 3,300,2,900, 2,850, 1,450, 1,360, 1,110 and 1,050 cm⁻¹ :

2. Preparation of 4-[N-methyl-N-(11-hydroxyundecyl)-amino]-benzaldehyde

11.6 g of the N-methyl-N-(11-hydroxyundecyl)amine obtained according toSection 1, 8 g of potassium carbonate powder, 7.18 g of4-fluorobenzaldehyde and 2 drops of the conventional and known phasetransfer catalyst Aliquat® 336 (fatty quaternary ammonium chloride) in50 ml of dimethylpropyleneurea were stirred for 72 hours at 95° C.Aliquat 336 is a commercial product and constitutesmethyl-trioctylammonium chloride. It is a mixture of C₈ - and C₁₀-chains, C₈ being predominant. It is used as a phase transfer catalystand liquid ion exchanger. The reaction mixture was then diluted with 700ml of water and extracted with three times 50 ml of a solvent mixture ofether and ethyl acetate in a volume ratio of 1:1. The combined extractswere washed with three times 50 ml of water and then dried with sodiumsulfate and, after the sodium sulfate had been separated off, wereevaporated down. The resulting residue was freed from unconvertedbenzaldehyde by drying at 60° C. under reduced pressure from an oilpump, this procedure being monitored by thin layer chromatography. Thedry product was purified by boiling with active carbon in acetone 12.45g of 4-[N-methyl-N-(11-hydroxyundecyl)]-amino]-benzaldehyde wereobtained, whose IR spectrum (KBr pellet) had bands at 3,400, 2,900,2,850, 1,660, 1,580, 1,520, 1,460, 1,440, 1,380, 1,310, 1,240, 1,160,1,050 and 820 cm⁻¹.

3. Preparation of4'-[N-methyl-N-(11-hydroxyundecyl)-amino]-benzaldehyde-4-nitrophenylhydrazone

A mixture of 8.62 g of4-[N-methyl-N-(11-hydroxyundecyl)-amino]-benzaldehyde, 4.33 g of4-nitrophenylhydrazine and 25 ml of glacial acetic acid were [sic]refluxed for 30 minutes and left to stand overnight at room temperature.70 ml of ice water were added to the resulting reaction mixture and themixture was stirred thoroughly After the water had been removed from thereaction mixture, the reaction product, which had now precipitated, wasseparated off and then subjected to preliminary purification by boilingwith active carbon in acetone. The prepurified product was then purifiedby flash chromatography on silica gel, a mixture of hexane and ethylacetate in a volume ratio of 6:4 being used as the mobile phase. A totalof 3.4 g of4'-N-methyl-N-(11-hydroxyundecyl)-amino]-benzaldehyde-4-nitrophenylhydrazonewere obtained, corresponding to a yield of 28% of theory. In its IRspectrum, this product, in the form of a KBr pellet, had bands at 3,400,3,250, 1,585, 1,510, 1,490, 1,460, 1,320, 1,290, 1,270, 1,170, 1,100,830 and 810 cm⁻¹.

4. Preparation of4'-[N-methyl-N-(11-methacryloyloxyundec-1-yl)-amino]-benzaldehyde-4-nitrophenylhydrazone

4.51 g of4'-[N-methyl-N-(11-hydroxyundecyl)amino]-benzaldehyde-4-nitrophenylhydrazonein 40 ml of chloroform were initially taken. 1.14 g of triethylamine and1.21 g of methacryloyl chloride, each in 10 ml of chloroform, were addeddropwise to this solution. Hydroquinone monomethyl ether, as astabilizer, was then added to the resulting reaction mixture, which wasthen refluxed for 7 hours. Thereafter, a further small amount oftriethylamine and methacryloyl chloride were metered in so that a 10 mol% excess of these two reactants resulted. The reaction mixture was thenrefluxed for a further 6 hours. The reaction mixture was cooled to roomtemperature, after which 150 ml of water were added. The organic phasewas separated off from the aqueous phase, washed with three times 40 mlof water, with three times 30 ml of 10% strength sodium bicarbonatesolution and then again with 30 ml of water and dried with sodiumsulfate. The sodium sulfate was separated off, after which the organicphase was evaporated down. If the IR the residue was again subjected tothe reaction conditions described above.

After the solvent had been removed from the residue, the latter waspurified by flash chromatography over silica gel using a solvent mixtureof ethyl acetate and hexane in a volume ratio of 3:7 and thenrecrystallized from a solvent mixture of heptane and dioxane in a volumeratio of 95:5.

1.52 g of4'-[N-methyl-N-(11-hydroxyundecyl)-amino]-benzaldehyde-4-nitrophenylhyirazonewere obtained. The product had the following physical properties: IRspectrum (KBr pellet): bands at 3,260, 2,900, 2,850, 1,700, 1,590,1,510, 1,495, 1,470, 1,320, 1,300, 1,275, 1,180, 1,110, 840 and 810 cm⁻¹; ¹ H nuclear magnetic resonance spectrum (400 MHz, CDCl₃,tetramethylsilane as internal standard), chemical shift δ (in ppm):1.3-1.6 (multiplet, 18 H), 1.9 (singlet, 3H), 3.0 (2H, unresolved), 3.36(2H, unresolved), 4.1 (triplet, 2H), 5.5 (singlet, 1H), 6.1 (singlet,1H), 6.6 (doublet, 2H), 7.1 (doublet, 2H), 7.5 (doublet, 2H), 7.7(singlet, 1H), 8.15 (doublet, 2H).

The chemically determined elemental composition corresponded to thetheoretical calculations: calculated: 68.5% C, 7.9% H, 11.0% N and 12.6%0; found: 67.9% C, 8.2% H, 10.2% N and 13.0% 0.

5. Preparation of the novel methacrylate copolymer

0.4 g of 4'-[N-methyl-N-(11-methacryloyloxyundecl-yl)-amino]-benzaldehyde-4-nitrophenylhydrazone, 0.266 g of n-octadecylmethacrylate and 0.007 g of azobisisobutyronitrile were dissolved in 15ml of analytically pure toluene. The resulting solution was degassed bypassing in nitrogen and then stirred at 70° C. for 72 hours undernitrogen, a further nine portions of 0.007 g of azobisisobutyronitrilebeing metered in during this time. The course of the reaction wasmonitored with the aid of gel permeation chromatography. After the endof the polymerization, the solution was filtered and the filtrate wasevaporated down to about 3 ml. The novel methacrylate copolymer was thenprecipitated in methanol and reprecipitated twice more from toluene withmethanol. 0.38 g of the novel methacrylate copolymer was obtained. Ithad a number average molecular weight M_(n) of 7,500.

The novel methacrylate copolymer was easy to process, transparent,homogeneous and laser-stable in the form of a thin film and verysuitable for the production of Langmuir-Blodgett films.

EXAMPLES 6 TO 8 Production of novel Langmuir-Blodgett films by theLangmuir-Blodgett technology

The novel methacrylate copolymer of Example 2 was used for carrying outExamples 6 to 8.

EXAMPLE 6 Production of a novel Langmuir-Blodgett multilayer from themethacrylate copolymer

Experimental method:

A solution having a concentration of 1 mg/ml of copolymer in purechloroform was applied to the surface of a Langmuir trough. A solidmonomolecular film was obtained by increasing the surface pressure bymeans of a movable barrier. At a surface pressure of 25 mN/m, the solidmonomolecular film was transferred to the surface of a cleaned siliconchip by vertically dipping in said chip and withdrawing it. The rate ofdipping was 4 mm/min, and the solid monomolecular film transferred in Ydeposition with a transfer ratio of virtually 1.0.

This process was repeated several times so that a Langmuir-Blodgettmultilayer resulted whose thickness, determined ellipsometrically in theconventional and known manner, increased linearly with the number oftransferred monolayers.

EXAMPLE 7 Production of a novel Langmuir-Blodgett multilayer whichcontains Langmuir-Blodgett monolayers of the methacrylate copolymer andof a polymer amphiphile in alternating sequence

Experimental method:

Example 6 was repeated, except that, after each application of a solidmonomolecular film of the copolymer, a solid monomolecular film of thepolymeric amphiphile ##STR9## was transferred in Y deposition.

EXAMPLE 8 Production of a novel Langmuir-Blodgett monolayers whichcontains Langmuir-Blodgett monolayers of the methacrylate copolymer andof a low molecular weight amphiphile in alternating sequence

Experimental method:

Example 7 was repeated, except that tricosenoic acid was used instead ofthe polymeric amphiphile.

The novel Langmuir-Blodgett multilayers produced according to Examples 6to 8 were of excellent quality and had a uniform thickness and virtuallyno film defects. They were all extremely stable to intense laserradiation. Among the Langmuir-Blodgett multilayers produced, on thebasis of their nonlinear optical properties that of Example 6 wassuitable, that of Example 8 particularly suitable and that of Example 7very particularly suitable as nonlinear optical materials for nonlinearoptical arrangements. The novel Langmuir-Blodgett multilayers of Example7 furthermore were mechanically extremely stable.

EXAMPLES 9 TO 14 Production of novel Langmuir-Blodgett films by theLangmuir-Blodgett technology

The novel methacrylate copolymer of Example 3 was used for carrying outExamples 9 and 10.

The novel methacrylate copolymer of Example 4 was used for carrying outExamples 11 and 12.

The novel methacrylate copolymer of Example 5 was used for carrying outExamples 13 and 14.

The novel Langmuir-Blodgett multilayers of Examples 9 to 14 wereproduced by the general experimental method stated in Example 6, exceptthat the temperature of the Langmuir trough was 15° C. and that asurface pressure of 20 mN/m was used in Examples 9, 11 and 13, and asurface pressure of 22 mN/m in Examples 10, 12 and 14.

The thickness of the novel Langmuir-Blodgett multilayers, determinedellipsometrically in a conventional and known manner, increased linearlywith the number of transferred monolayers.

The novel Langmuir-Blodgett multilayers produced according to Examples 9to 14 were also of excellent quality and had a uniform thickness andvirtually no film defects. They were all extremely stable to intenselaser radiation and were therefore very suitable as nonlinear opticalmaterials for nonlinear optical arrangements.

We claim:
 1. A (meth)acrylate copolymer which contains, as polymerizedunits,A) one or more (meth)acrylates or (meth)acrylamides having secondorder nonlinear optical properties and the formula ##STR10## where R shydrogen or methyl, X is a flexible spacer, which may or may not bepresent, Y is a divalent group having electron donor activity capable ofdonating electrons to the easily polarizable conjugated π-electronsystem of Z and Z is a noncentrosymmetic radical containing an easilypolarizible conjugated π-electron system and one or more nitro,trifluoromethyl, cyano, or fulven-6-yl groups as electron acceptorgroups capable of accepting electrons directly from -YZ, and B) one ormore (meth) acrylates of alkanols where the alkyl radical is of 10 to 30carbon atoms, the molar ratio of A to B being from 1:0.5 to 1:5.
 2. A(meth)acrylate copolymer as claimed in claim 1, wherein the length ofthe alkyl ester radicals (--COO--alkyl) of the (meth)acrylates (B) isapproximately the same length as the radicals --CO--X--Y--Z or--CO--Y--Z of the (meth)acrylates or (methacrylamides (A) of the formulaI.
 3. A (meth)acrylate copolymer as claimed i claim 1, which containsexclusively one or more (meth)acrylates or (meth)acrylamides (A) and oneor more (meth)acrylates (B) as polymerized units.
 4. A nonlinear opticalmaterial which comprises a (meth)acrylate copolymer as claimed inclaim
 1. 5. A Langmuir-Blodgett film in which the film-forming groups ormolecules are all uniformly spatially oriented and which comprises oneor more solid monomolecular Langmuir-Blodgett films comprising the(meth)acrylate copolymer as claimed in claim
 1. 6. A nonlinear opticalarrangement which contains one or more substrates and one or moreLangmuir-Blodgett films as claimed in claim
 5. 7. A nonlinear opticalarrangement which has at least one substrate and at least one filmcomprising the (meth)acrylate copolymer as claimed in claim
 1. 8. Aprocess for the uniform spatial orientation of organic radicals, whereinfirst(1) a (meth)acrylate copolymer as claimed in claim 1 is preparedand said copolymer is then (2) formed into at least one solidmonomolecular Langmuir-Blodgett film.